Batteries - at lower charge

15th of October 2010

Recyclable batteries that last longer, require less maintenance and have shorter recharging times can help to bring down the cost of running a cleaning machine. But can a battery-powered machine compete with its mains-powered counterpart in terms of cost-effectiveness? Ann Laffeaty finds out.

Battery-powered machines have become increasingly viable over the past few years. There is no doubting their usefulness in any environment where a cable is impractical. Meanwhile the market is changing rapidly and today’s batteries last longer, perform better and accept a charge faster than ever before. But how do they compare with mains-powered machines and propane options in terms of cost?

Modern batteries and chargers are much more effective – and cost-effective - than they were in the past according to Optima Batteries’ business development manager Hans de Jong. “Today’s smaller, lighter batteries result in lower transport costs and mean that less energy is needed to run the machine,” he said.

Today’s batteries are also more efficient because their internal resistance is lower, says de Jong. “Internal resistance determines how effective a battery is at supplying energy and taking a charge,” he said. “The most commonly-used battery – the Gel battery - has a very high internal resistance and is not very efficient at taking a charge or delivering power.

“The Optima spiral cell battery has the lowest internal resistance in the industry and we believe it to be the most efficient battery on the market today. A battery with a low internal resistance is more cost-effective because it gives you a longer run-time than a Gel battery can deliver.”

He claims the Optima Yellow Top 4.2 has an internal resistance of 2.8 which is three times lower than that of a similar-sized Gel battery. “This means you would need to recharge a battery for longer using a lower current and it would be less effective at delivering power,” said de Jong. “Our battery could also recharge in half the time depending on current.”

The higher the cycle life, the more cost-effective the battery says de Jong. “You can take 50 per cent out of the Optima battery and it will still supply 1,000 cycles,” he said. “We are working towards increasing the cycle life even more.”

However his surprise conclusion is that mains-powered cleaning machines still have the edge over battery-powered alternatives in terms of cost. “If you look at the energy side I think cleaning machines connected to the mains are more cost-effective,” said de Jong. “When you use a battery there are going to be some losses: a charger is not 100 per cent effective, for example, and some of the energy will be turned into heat.

“The problem is that you can’t always clean with a machine attached to a cable - especially when the public is around. If you have a machine running in an office, for example, people might trip over the lead. In any case a cable only has a certain length and reach which means that a battery-powered machine is always more flexible.”

Enersys’ monobloc European sales manager Chris Walsh agrees battery-powered machines are often the only option – and in such cases a cost comparison between these and alternative-powered machines is irrelevant. “IC engines are rarely acceptable indoors, while mains cables are often banned as they represent a trip hazard,” he said. “The choice is more usually made between differing battery technologies with the decision being based on cost and health and safety considerations as well as application.”

For example, said Walsh, in an industrial environment it might be more cost-effective to use a flooded battery whereas in a retail or office environment a 'valve regulated' option such as a Gel battery or the company’s own fast/opportunity charge Hawker XFC Flex might be more appropriate.

“Conventional ‘valve regulated’ batteries have been used in these applications for some years since they need little maintenance, leak no acid and generate very little hydrogen gas when they are being charged,” he said. “However they offer less running time per charge than an equivalent-sized flooded battery and cannot be opportunity charged. They also need a longer uninterrupted recharge after use - typically eight to 12 hours.”

He claims that 'fast charge' batteries are a step-change for traction batteries since they offer a lower cost of ownership due to their advanced technology and higher cyclic life. “This means you need fewer sets of batteries in the machine’s lifetime.”

General manager of Battery Supplies Alexander de Soete says batteries need to be compared with other power sources over a long-term period to assess the cost-savings they can achieve. “The maintenance costs of a battery-operated machine tend to be lower in general than those of a machine running on diesel or petrol,” he said.

“The efficiency of batteries has also improved a great deal over the years. Deep-cycle batteries and traction batteries with tubular positive plates offer a longer life and a better charge than the older generation of cyclic batteries.

“Products such as Gel and AGM batteries no longer require any maintenance which is a major advantage, because people tend to forget that batteries need to be topped up with water from time to time.”

He said the company’s lead-acid batteries were the most cost-effective products offered by Battery Supplies in terms of price, durability and running time. And there are other, hidden savings to be made via an optimum combination of charger and batteries, according to de Soete.

“If you use a high-frequency charger that is specifically adapted for use with your batteries you will increase the battery life,” he said. “Also, a compatible charger will control the voltage of the batteries and charge only what is required. This means you will be using less energy to charge the batteries while also reducing heating and water consumption – which will all result in lower costs.”

Vice-president marketing of the Trojan Battery Company Elke Hirschman also feels it is important to look at the hidden costs of running a cleaning machine before making an informed choice. “An electrical power solution might seem less expensive at first, but it presents a number of disadvantages over battery power,” she said. “Using a power cord means less flexibility while performing the cleaning job since the operator will have to continuously plug the cord in and out while moving the floor machine over different sections.

“In a large space such as an airport or hospital this can cause not only inconvenience due to frequent labour interruptions, but also increased costs due to longer labour times and use of manpower.”

Trojan manufactures a range of flooded deep cycle, Cycling AGM and Deep-Cycle Gel products. According to Hirschman, modern breakthroughs such as increased durability, lower maintenance and shorter recharging times have greatly increased the cost-effectiveness of battery power.

“These all result in more uptime for the floor machine as well as lower maintenance costs and reduced labour time,” she said. “Typically a floor machine will run for between six and eight hours. Any downtime can bring additional costs which is why it is critical to use a high quality, durable battery to operate floor machines as cost-efficiently as possible.”

She says maintenance-free AGM and gel batteries in particular help to reduce labour costs because they require no watering. “Proper care and maintenance of a battery can significantly increase the life of a flooded battery,” she added. “When comparing batteries to electric power, a battery stands out as the preferred choice due to flexibility.”

So what does the future hold for battery-powered machines? According to Hirschman: “OEM manufacturers are incorporating more technological advances into their manufactured products to make ownership and operation more productive and cost-effective. Battery manufacturers are continuously seeking ways to improve productivity, lower maintenance costs and improve cost-effectiveness.”

Chris Walsh from Enersys believes future technologies such as lithium-ion batteries may bring cost savings since they will result in smaller, lighter batteries. “But they are far from cost-effective at the moment due to their much higher capital costs, and they are also difficult to transport for safety reasons,” he said. “For now the best option seems to be the newer fast/opportunity charge technologies.”

And Optima Batteries’ Hans de Jong says the industry is moving increasingly towards the AGM battery for reasons of safety and cost. “The advantage of Gel and AGM batteries is that they don’t need any maintenance because they are completely sealed,” he said. “You still have to top up the majority of flooded batteries. Also, you are not permitted to recharge flooded batteries inside without measuring the level of ventilation first. This means that more investment is needed because you have to create a room with the right ventilation conditions in which to recharge them.”

He feels that lead acid batteries have developed as far as they can. “The latest direction is towards lithium-ion batteries but these are not very cost-effective at the moment,” he said. “It will take a few more years before these become cost-effective - but we are working on it.”